In recent years, information processors, typified by computers and mobile communication systems, have dramatically achieved higher information processing speeds, size reductions, and a larger number of functions. Such improvements in the performance of information processors have been realized mainly with increasing packing densities, speeds, and performance of semiconductor devices.
Semiconductor devices are conventionally mounted on alumina insulating substrates, which are fired at 1,500° C. to 1,600° C. Accordingly, high-melting metals such as Mo, Mo—Ni, and W must be used as the material for patterned conductors to co-fire the insulating substrates with the patterned conductors. Such high-melting metals, however, have high resistivity and thus pose difficulty in sufficiently exploiting the performance of semiconductor devices for higher information processing speeds and higher processing signal frequencies.
A variety of ceramic substrate compositions have been developed which can be co-fired with low-melting metals having low resistivity, such as Ag and Cu. An example is a ceramic substrate composition prepared by adding Al2O3 to a CaO—SiO2—Al2O3—B2O3-based glass (see Patent Document 1). Patent Document 1: Japanese Examined Patent Application Publication No. 3-53269